Equipe Epigénétique et Formation du Zygote

The formation of a diploid zygote from two highly different gametes is a critical aspect of sexual reproduction in animals. Notably, the transmission of the paternal genome implies unique chromatin reorganization events that take place during spermiogenesis and at fertilization. Our group studies these processes at the functional level using Drosophila melanogaster as main model organism, with a special interest in understanding the evolutionary forces at play during the delicate integration of the paternal genome in its new cellular environment.
.
We currently develop three main research themes :
.

 Evolution and function of sperm chromosomal proteins

In most species, the formation of mature sperm nuclei involves the massive replacement of nucleosomes with Sperm Nuclear Basic proteins (SNBPs), such as mammalian protamines, for instance. In contrast to highly conserved somatic core histones, SNBPs are fast evolving proteins that compact sperm DNA in a unique manner. Drosophila is an excellent model to study SNBP function and evolution, as well as the mechanisms involved in their replacement with maternally-provided histones at fertilization.
.
.
.
.

 Spermatogenesis and genetic conflicts

Several classical examples of genetic conflicts are described in Drosophila melanogaster and its sibling species D. simulans. They generally result in the non-Mendelian transmission of certain chromosomes, sometimes in spectacular proportions.
In D. melanogaster, the Segregation Distorter system is a famous example of selfish transmission of an autosome at the expense of its homolog, and manifests itself in post-meiotic spermatids. In D. simulans, Sex Ratio distorters affect the survival of Y-bearing spermatids following the second meiotic division, resulting in highly skewed sex ratio towards females.
The molecular elucidation of these genetic conflicts can reveal important aspects of chromosome organization during male gametogenesis.
.
.
.
.

 Wolbachia and Cytoplasmic Incompatibility

Wolbachia is an endosymbiotic bacteria which is vastly distributed in arthropods and is known for its ability to manipulate the reproduction of its host to favor its own vertical transmission. In flies, Wolbachia causes a sterility syndrome known as Cytoplasmic Incompatibility (CI). CI occurs when sperm from infected males fertilize uninfected eggs. Paternal chromosomes in these eggs appear unable to properly divide during the first zygotic cycle but the molecular bases of this intriguing phenotype remain elusive. We are interested in understanding how Wolbachia interferes with the remodeling of paternal chromatin at fertilization in Drosophila, as well as in the parasitoid wasp Nasonia vitripennis.